This invention relates to an improvement applicable to the structure of a semiconductor device which includes one or more semiconductor pellets having at least one semiconductor device element disposed therein and being mounted on a printed circuit board and being covered by a resin layer and to a method for producing a semiconductor device free from drawbacks accompanying the structure of a semiconductor device which includes one or more semiconductor pellets having at least one semiconductor device element disposed therein and mounted on a printed circuit board and being covered by a resin layer.
Available in the prior art is a semiconductor device illustrated in FIG. 1. Referring to the drawing, a semiconductor pellet 22 in which at least one semiconductor device element has been produced, is mounted on a printed circuit board 11 made of a glass epoxy resin complex et al. and which has bonding pads 20 thereon connected by bonding wires 26 with the counter parts 24 produced on the semiconductor pellets 22, which are covered by a resin layer 28. The printed circuit board 11 has solder bump electrodes 16 produced thereunder. When such a semiconductor device is mounted on a larger printed circuit board or a mother board 14, as is shown in FIG. 2, the solder bump electrodes 16 are connected, employing a melting process, with corresponding electrodes 50 printed on the larger printed circuit board or the mother board 14.
The foregoing semiconductor device available in the prior art is inevitably accompanied by drawbacks tabulated below.
1. The adhesion is likely to be broken for the interface between the semiconductor pellets 22 and the resin layer 28, due to thermal stress caused by the difference in the coefficients of thermal expansion. This drawback readily happens during the process for mounting the semiconductor device on the larger printed circuit board or the mother board. This drawback readily allows humidity to contact metal parts of the circuit of the semiconductor pellets 22, resultantly causing the metal parts of the circuit to be corroded.
2. The heat generated in the semiconductor pellets 22 is dissipated toward the larger printed circuit board or the mother board through the printed circuit board 11 made of the glass epoxy resin complex et al. of which the thermal conductivity is less, resultantly causing a less grade of the thermal dissipation efficiency for the semiconductor device having the foregoing structure. This drawback readily causes a remarkable rate of delay in the operation speed of the semiconductor device.
Accordingly, an object of this invention is to provide a variety of semiconductor devices for which the hermetic seal is reliable for the interface between one or more semiconductor pellets having one or more semiconductor device element disposed therein and being arranged therein and a resin layer which covers the semiconductor pellet or pellets, resultantly effectively preventing humidity from contacting the metal parts of the circuits of the semiconductor device and sufficiently protecting the metal parts of the circuits from potential corrosion and for which the thermal conductivity has been improved, resultantly preventing a delay in operation speed from occurring due to a temperature rise thereof.
The other object of this invention is to provide a method for producing the variety of semiconductor devices having the foregoing advantages.
To achieve the foregoing object, the semiconductor device in accordance with this invention is based on a concept that one or more semiconductor pellets having one or more semiconductor device element disposed therein are arranged on the bottom surface of a recess produced along a surface of a semiconductor plate having wirings arranged on the surface of the semiconductor plate, the wirings extending toward the surface of the recess, and the recess being buried with a layer of a resin which is inclined to inflate, while it is hardened, resultantly producing a mechanical stress in the resin layer in a direction to expand the resin layer toward the side wall of the recess engraved in the semiconductor plate, resultantly preventing breakage from happening for an interface between the side wall of the recess engraved in the semiconductor plate and the surface of the resin layer contacting the side wall, and remarkably improving the thermal conductivity efficiency to reduce the magnitude of a temperature rise of the semiconductor device, resultantly preventing a delay from happening for the operation speed of the semiconductor device.
Various embodiments itemized below are presented.
1. The connection between the bonding pads of the semiconductor pellet or pellets and the wirings can be made by bump electrodes.
2. The recess of the semiconductor plate can be made to have a multiple step.
3. The rear surface of the semiconductor plate can be provided with plural cooling grooves arranged in parallel to each other, arranged in plural crosses or arranged in some other geometrical patterns.
4. The rear surface of the semiconductor plate can be provided with a metal plate heat sink.
To achieve the foregoing other object of this invention, the method for producing the variety of semiconductor devices of this invention has a step for producing a recess along one surface of a semiconductor plate, a step for producing wirings extending along a surface of the recess of the semiconductor plate and along one surface of the semiconductor plate, either two steps consisting of a step for placing at least one semiconductor pellet having at least one semiconductor device element disposed therein and having bonding pads arranged thereon and a step for connecting the bonding pads with the wirings employing bonding wires, or one step for placing at least one semiconductor pellet having at least one semiconductor device element disposed therein and having bonding pads arranged thereon, in a face down position to connect the bonding pads with the wirings, a step for burying the recess with a resin, and a step for producing plural electrodes along the one surface of the semiconductor plate to connect the electrodes with the wirings.